1. Field of the Invention
The present invention relates to epoxy resin compositions, and more specifically, the present invention relates to epoxy resin compositions including diglycidyl ethers of dihydroxydiphenyl cycloalkane compounds and advanced resin compositions and derivatives made from the epoxy resin compositions. The epoxy resin compositions may be used in a variety of applications end uses such as powder coatings, composites and electrical laminates.
2. Description of Background and Related Art
Thermoset resins, such as epoxy resins (“epoxies”), having good thermal resistant properties, are desirable for many applications such as electrical laminates, coatings, powder coatings, castings, and composites. Three desirable properties for these aryl glycidyl ethers are high glass transition temperature (Tg greater than 190° C. by dynamic mechanical thermal analysis with dicyandiamide cure), low monomer viscosity (less than 200 mPa-s at 150° C.), and high epoxy equivalent weight (EEW). Epoxies of the present invention exhibit viscosities as low as 120 mPa-s and the dicyandiamide-cured thermosets have Tgs up to 202° C. and EEWs of greater than 190 grams/equivalent (g/eq).
High Tgs are needed for applications where the thermoset will be exposed to high temperature, for example as a coating steel pipe used for transporting hot oil. The properties of the thermoset degrade precipitously above the temperature of the Tg. Resins having a low viscosity make it easier to process them into a finished part, and easy processability is always desirable. Also, adhesion to metals and glass is usually better for low viscosity thermosets because wetting of the complex microstructure of the substrate is better. Finally, epoxy resins with high EEWs give thermosets with a relatively low concentration of hydroxyls in the backbone. Hydroxyls are formed during typically curing reactions of epoxy resins, such as with dicyandiamide, a multifunctional amine. There is a direct relationship between hydroxyl concentration in a thermoset and water absorption. High water absorption is undesirable in most applications because it can reduce adhesion and degrade other properties.
There are many aryl glycidyl ethers that achieve these properties individually, but not that meet them all properties simultaneously. This balance of properties is difficult to achieve. For example, one common strategy for high Tg is to use polyglycidyl ethers of highly functional polyphenols, especially phenol formaldehyde novolacs which are known as epoxy novolacs. However, examples of such novolacs that have viscosities of less than 200 cP are not capable of achieving high Tgs comparable to the epoxy resins of the present invention. For example, D.E.N.™ 438 (trademark of The Dow Chemical Company), an industry standard epoxy novolac, has a viscosity of <200 mPa-s but the Tg of the dicyandiamide-cured thermoset is only 173° C.
Accordingly, there is still a need in the industry to develop new thermoset resins that are difunctional and provide thermosets with a balance of properties including high Tg (>190° C.), low monomer viscosity (<150 mPa-s at 150° C.) and high EEW (>190 g/eq).